Systems and methods for treating vertebral bodies

ABSTRACT

Systems and methods treat at least two vertebral bodies in a spinal column. The systems and methods make use of first and second tool assemblies operable to treat an interior region of, respectively, a first vertebral body and a second vertebral body in the spinal column. The systems and methods provide directions for operating the first and second tool assemblies to treat the first and second vertebral bodies, at least for a portion of time, concurrently.

RELATED APPLICATIONS

[0001] This application is a division of co-pending application Ser. No.09/597,646 filed Jun. 20, 2000, which is a continuation-in-part ofapplication Ser. No. 09/134,323, filed Aug. 14, 1998, and entitled“Systems and Methods for Placing Materials into Bone”.

FIELD OF THE INVENTION

[0002] The invention generally relates to the treatment of boneconditions in humans and other animals.

BACKGROUND OF THE INVENTION

[0003] The deployment of expandable structures, generically called“balloons,” into cancellous bone is known. For example, U.S. Pat. Nos.4,969,888 and 5,108,404 disclose apparatus and methods using expandablestructures in cancellous bone for the fixation of fractures or otherosteoporotic and non-osteoporotic conditions of human and animal bones.

SUMMARY OF THE INVENTION

[0004] The invention provides systems and methods for treating bone.

[0005] According to one aspect of the invention, the systems and methodstreat at least two vertebral bodies in a spinal column. The systems andmethods make use of first and second tool assemblies operable to treatan interior region of, respectively, a first vertebral body and a secondvertebral body in the spinal column. The systems and methods providedirections for operating the first and second tool assemblies to treatthe first and second vertebral bodies, at least for a portion of time,concurrently.

[0006] According to another aspect of the invention, the systems andmethods employ a device for compacting cancellous bone. The devicecomprises a wall adapted to be inserted into bone and undergo expansionin cancellous bone to compact cancellous bone. The systems and methodsinclude a cortical bone plugging material inserted into the bone eitherbefore or after expansion of the device.

[0007] According to another aspect of the invention, the systems andmethods include an instrument introducer defining an access passage intocancellous bone through cortical bone. The systems and methods alsoinclude an instrument including a distal body portion having a dimensionsized for advancement through the access passage to penetrate cancellousbone. In one embodiment, the instrument includes a proximal stop havinga dimension greater than the access passage and having a location toprevent penetration of the distal body portion beyond a selected depthin cancellous bone. In another embodiment, the distal body regionincludes a blunt terminus to tactilely indicate contact with corticalbone without breaching the cortical bone.

[0008] According to another aspect of the invention, the systems andmethods use an instrument introducer defining an access passage intocancellous bone through cortical bone. A gripping device restes on anexterior skin surface and engages the instrument introducer to maintainthe instrument introducer in a desired orientation.

[0009] According to another aspect of the invention, the systems andmethods include a device adapted to be inserted into bone in a collapsedcondition and thereafter expanded to form a cavity in cancellous bone.The systems and methods employ a fluid transport passage to convey fluidfrom a source into the cavity to resist formation of a vacuum inside thecavity as the device is returned to the collapsed condition andwithdrawn from bone.

[0010] According to another aspect of the invention, the systems andmethods include a device adapted to be inserted into bone and undergoexpansion in cancellous bone. A transport passage conveys an expansionmedium into the device. The expansion medium includes an amount ofmaterial to enable visualization of the expansion. The systems andmethods include an exchanger assembly communicating with the transportpassage and operating to reduce the amount of material present in theexpansion medium within the device.

[0011] Another aspect of the invention provides systems and methods forforming an opening in cortical bone. In one embodiment, the systems andmethods employ a support body including a flexible shaft portion. Acortical bone cutting element is carried on the flexible shaft portion.The element operates to form an opening in cortical body in response toapplication of force. In another embodiment, a cortical bone cuttingelement is carried on a support body to form an opening into the bone.An expandable structure also carried on the support body and adapted tobe inserted through the opening and expanded to form a cavity-incancellous bone.

[0012] Features and advantages of the various aspects of the inventionare set forth in the following Description and Drawings, as well as inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a lateral view of a human spinal column;

[0014]FIG. 2 is a representative coronal view, with portions broken awayand in section, of a human vertebral body, taken generally along line2-2 in FIG. 1;

[0015]FIG. 3 is a lateral view, with portions broken away and insection, of several vertebral bodies, which are part of the spinalcolumn shown in FIG. 1;

[0016]FIG. 4 is a plan view of a tool which carries at its distal end anexpandable structure, which, in use, compresses cancellous bone, thestructure being shown in a collapsed condition;

[0017]FIG. 5 is enlarged side view of the expandable structure carriedby the tool shown in FIG. 4;

[0018]FIG. 6 is a coronal view of the vertebral body shown in FIG. 2,with a single tool shown in FIGS. 4 and 5 deployed through a lateralaccess in a collapsed condition;

[0019]FIG. 7 is a coronal view of the vertebral body and tool shown inFIG. 6, with the tool in an expanded condition to compress cancellousbone and form a cavity;

[0020]FIG. 8 is a coronal view of the vertebral body shown in FIGS. 6and 7, with the tool removed after formation of the cavity;

[0021]FIG. 9A is a coronal view of the vertebral body shown in FIGS. 8,with the cavity filled with a material that strengthens the vertebralbody;

[0022]FIG. 9B depicts an alternate method of filling a cavity within avertebral body;

[0023]FIG. 9C depicts the vertebral body of FIG. 9B, wherein the cavityis approximately half-filled with material;

[0024]FIG. 9D depicts the vertebral body of FIG. 9B, wherein the cavityis substantially filled with material;

[0025]FIG. 10 is a coronal view of the vertebral body shown in FIG. 2,with two tools shown in FIGS. 4 and 5 deployed through bilateralaccesses and in an expanded condition to compress cancellous bone andform adjoining, generally symmetric cavities;

[0026]FIG. 11 is a coronal view of the vertebral body shown in FIG. 10,with the tools removed after formation of the generally symmetriccavities and the cavities filled with a material that strengthens thevertebral body;

[0027]FIG. 12 is a coronal view of the vertebral body shown in FIG. 10,with the tools removed after formation of generally asymmetric cavities;

[0028]FIG. 13 is a anterior sectional view of three adjacent vertebralbodies, with six tools shown in FIGS. 4 and 5 deployed in collapsedconditions through two lateral accesses in each vertebral body;

[0029]FIGS. 14A to 14D are schematic anterior views of one of thevertebral bodies shown in FIG. 13, showing the alternating, step wiseapplication of pressure to the expandable structures to compresscancellous bone and form adjacent cavities;

[0030]FIGS. 15A and 15B are schematic anterior views of one of thevertebral bodies shown in FIGS. 14A to 14D, depicting the alternatingsequence of filling the adjacent cavities with a material to strengththe vertebral body;

[0031]FIGS. 16A to 16I are coronal views of a vertebral body as shown inFIGS. 14A to 14D and 15A and 15B, showing tools deployed to create alateral access to compress cancellous bone in a vertebral body to forman interior cavity, which is filled with a material to strengthen thevertebral body;

[0032]FIG. 17 is an exploded side section view of a reduced diameterobturator instrument with associated centering sleeve, which can bedeployed to create access in a vertebral body, particularly through apedicle;

[0033]FIG. 18A is a side section view of a drill bit instrument that canbe deployed to create access to a vertebral body, the drill bitinstrument having a flexible shaft and deployed through a cannulainstrument having a deflected end;

[0034]FIG. 18B is a side view of a drill bit instrument that can bedeployed to create access to a vertebral body, the drill bit instrumenthaving a flexible shaft and deployed over a guide wire having adeflected end;

[0035]FIG. 18C is a side view of a drill bit instrument that can bedeployed to create access to a vertebral body, the drill bit instrumenthaving a flexible shaft and including steering wires to deflect itsdistal end;

[0036]FIG. 19 is a coronal view of a vertebral body showing thedeployment of a spinal needle tool in a manner that creates a breach inan anterior cortical wall of the vertebral body;

[0037]FIG. 20A is an enlarged side view of a drill bit instrument havinga mechanical stop to prevent breach of an anterior cortical wall of thevertebral body;

[0038]FIG. 20B is an enlarged side view of a cortical wall probe thatcan be deployed to gauge the interior dimensions of a vertebral bodywithout breaching an anterior cortical wall of the vertebral body;

[0039]FIG. 21 is coronal view of a vertebral body with an expandablestructure deployed and expanded, showing the introduction of a liquid toprevent formation of a vacuum upon the subsequent deflation and removalof the structure;

[0040]FIG. 22A is a side view of a tool to introduce material into acavity formed in cancellous bone, with a nozzle having a stepped profileto reduce overall fluid resistance;

[0041]FIG. 22B is a side view of a tool to introduce material into acavity formed in cancellous bone, with a nozzle having a tapered profileto reduce overall fluid resistance;

[0042]FIG. 22C is a side view of a tool to introduce material into acavity formed in cancellous bone, with a nozzle having a reducedinterior profile to reduce overall fluid resistance;

[0043]FIG. 23 are top views of kits which hold, prior to use, thevarious instruments and tools usable to create multiple access paths ina single vertebral body, to compact cancellous bone and form a cavity tobe filled with a material, as generally shown in FIGS. 16A to 16I;

[0044]FIGS. 24A to 24C are coronal views of a vertebral body, showing asmall expandable body deployed through a needle to create a smallcavity, and the injection of a filling material under pressure throughthe needle to fill and enlarge the cavity to strengthen the vertebralbody;

[0045]FIG. 25 is an enlarged side section view of an expandable bodycarried at the end of a catheter tube, which further includes anintegrated drill bit instrument;

[0046]FIG. 26A is a perspective view of one embodiment of a lockingdevice for a cannula instrument;

[0047]FIG. 26B is a perspective view of another embodiment of a lockingdevice for a cannula instrument;

[0048]FIG. 27 is a perspective view of a composite tool that includes atrocar and a cannula instrument;

[0049]FIG. 28 is a perspective view of the composite instrument shown inFIG. 27, with the trocar separated from the cannula instrument;

[0050]FIG. 29A is a perspective view of a hand engaging the compositehandle of the tool shown in FIG. 27;

[0051]FIG. 29B is a perspective view of a hand engaging the handle ofthe cannula instrument when separated from the trocar;

[0052]FIG. 30 is a top view showing deployment of the compositeinstrument shown in FIG. 27 in a vertebral body, by using the compositehandle to apply an axial and/or torsional force;

[0053]FIG. 31 is a top view of the vertebral body, showing deployment ofa drill bit through a cannula instrument, which forms a part of thecomposite tool shown in FIG. 27; and

[0054]FIG. 32 depicts an exchange chamber for replacing and/or dilutingthe radiopaque medium within a structure with a partially-radiopaque orradiopaque-free medium;

[0055]FIG. 33 is an exploded perspective view of a cannula and materialintroducing device, which embodies features of the invention.

[0056] The invention may be embodied in several forms without departingfrom its spirit or essential characteristics. The scope of the inventionis defined in the appended claims, rather than in the specificdescription preceding them. All embodiments that fall within the meaningand range of equivalency of the claims are therefore intended to beembraced by the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] This Specification describes new systems and methods to treatbones using expandable bodies. The use of expandable bodies to treatbones is generally disclosed in U.S. Pat. Nos. 4,969,888 and 5,108,404,which are incorporated herein by reference. Improvements in this regardare disclosed in U.S. patent application, Ser. No. 08/188,224, filedJan. 26, 1994; U.S. patent application Ser. No. 08/485,394, filed Jun.7, 1995; and U.S. patent application Ser. No. 08/659,678, filed Jun. 5,1996, which are each incorporated herein by reference.

[0058] The new systems and methods will be described with regard to thetreatment of vertebral bodies. It should be appreciated, however, thesystems and methods so described are not limited in their application tovertebrae. The systems and methods are applicable to the treatment ofdiverse bone types, including, but not limited to, such bones as theradius, the humerus, the femur, the tibia, or the calcanus.

[0059] I. Vertebral Bodies

[0060] As FIG. 1 shows, the spinal column 10 comprises a number ofuniquely shaped bones, called the vertebrae 12, a sacrum 14, and acoccyx 16(also called the tail bone). The number of vertebrae 12 thatmake up the spinal column 10 depends upon the species of animal. In ahuman (which FIG. 1 shows), there are twenty-four vertebrae 12,comprising seven cervical vertebrae 18, twelve thoracic vertebrae 20,and five lumbar vertebrae 22.

[0061] When viewed from the side, as FIG. 1 shows, the spinal column 10forms an S-shaped curve. The curve serves to support the head, which isheavy. In four-footed animals, the curve of the spine is simpler.

[0062] As FIGS. 1 to 3 show, each vertebra 12 includes a vertebral body26, which extends on the anterior (i.e., front or chest) side of thevertebra 12. As FIGS. 1 to 3 show, the vertebral body 26 is in the shapeof an oval disk. As FIGS. 2 and 3 show, the vertebral body 26 includesan exterior formed from compact cortical bone 28. The cortical bone 28encloses an interior volume 30 of reticulated cancellous, or spongy,bone 32(also called medullary bone or trabecular bone). A “cushion,”called an intervertebral disk 34, is located between the vertebralbodies 26.

[0063] An opening, called the vertebral foramen 36, is located on theposterior (i.e., back) side of each vertebra 12. The spinal ganglion 39pass through the foramen 36. The spinal cord 38 passes through thespinal canal 37.

[0064] The vertebral arch 40 surrounds the spinal canal 37. The pedicle42 of the vertebral arch 40 adjoins the vertebral body 26. The spinousprocess 44 extends from the posterior of the vertebral arch 40, as dothe left and right transverse processes 46.

[0065] II. Treatment of Vertebral Bodies

[0066] A. Lateral Access

[0067] Access to a vertebral body can be accomplished from manydifferent directions, depending upon the targeted location within thevertebral body, the intervening anatomy, and the desired complexity ofthe procedure. For example, access can also be obtained through apedicle 42 (transpedicular), outside of a pedicle (extrapedicular),along either side of the vertebral body (posterolateral), laterally oranteriorly. In addition, such approaches can be used with a closed,minimally invasive procedure or with an open procedure.

[0068]FIG. 4 shows a tool 48 for preventing or treating compressionfracture or collapse of a vertebral body using an expandable body.

[0069] The tool 48 includes a catheter tube 50 having a proximal and adistal end, respectively 52 and 54. The distal end 54 carries astructure 56 having an expandable exterior wall 58. FIG. 4 shows thestructure 56 with the wall 58 in a collapsed geometry. FIG. 5 shows thestructure 56 in an expanded geometry.

[0070] The collapsed geometry permits insertion of the structure 56 intothe interior volume 30 of a targeted vertebral body 26, as FIG. 6 shows.The structure 56 can be introduced into the interior volume 30 invarious ways. FIG. 6 shows the insertion of the structure 56 through asingle lateral access, which extends through a lateral side of thevertebral body 12.

[0071] Lateral access is indicated, for example, if a compressionfracture has collapsed the vertebral body 26 below the plane of thepedicle 42, or for other reasons based upon the preference of thephysician. Lateral access can be performed either with a closed,mininimally invasive procedure or with an open procedure. Of course,depending upon the intervening anatomy, well known in the art, lateralaccess may not be the optimal access path for treatment of vertebrae atall levels of the spine.

[0072] The catheter tube 50 includes an interior lumen 80 (see FIG. 4).The lumen 80 is coupled at the proximal end of the catheter tube 50 to apressurized source of fluid, e.g., saline. A syringe containing thefluid can comprise the pressure source. The lumen 80 conveys the fluidinto the structure 56 under pressure. As a result, the wall 58 expands,as FIGS. 5 and 7 show.

[0073] The fluid is preferably rendered radiopaque, to facilitatevisualization as it enters the structure 56. For example, Renografin™can be used for this purpose. Because the fluid is radiopaque, expansionof the structure 56 can be monitored fluoroscopically or under CTvisualization. Using real time MRI, the structure 56 may be filled withsterile water, saline solution, or sugar solution, free of a radiopaquematerial. If desired, other types of visualization could be used, withthe tool 48 carrying compatible reference markers. Alternatively, thestructure could incorporate a radiopaque material within the material ofthe structure, or the structure could be painted or “dusted” with aradiopaque material.

[0074] Expansion of the wall 58 enlarges the structure 56, desirablycompacting cancellous bone 32 within the interior volume 30 (see FIG. 7)and/or causing desired displacement of cortical bone. The compaction ofcancellous bone 32 forms a cavity 60 in the interior volume 30 of thevertebral body 26 (see FIG. 8). As will be described later, a fillingmaterial 62 can be safely and easily introduced into the cavity 60 whichthe compacted cancellous bone 32 forms. In one embodiment, expansion ofthe structure 56 desirably forms a region of compacted cancellous bonewhich substantially surrounds the cavity 60. This region desirablycomprises a barrier which limits leakage of the filling material 62outside the vertebral body 26. In an alternate embodiment, the expansionof the structure 56 desirably presses cancellous bone 32 into smallfractures which may be present in cortical bone, thereby reducing thepossibility of the filling material 62 exiting through the corticalwall. In another alternative embodiment, the expansion of the structure56 desirably flattens veins in the vertebral body that pass through thecortical wall (e.g., the basivertebral vein), resulting in lessopportunity for filling material 62 to extravazate outside the vertebralbody through the venous structure in the cortical wall. Alternatively,expansion of the structure 56 will compress less dense and/or weakerregions of the cancellous bone, which desirably increases the averagedensity and/or overall strength of the remaining cancellous bone.

[0075] The compaction of cancellous bone by the structure 56 can alsoexert interior force upon cortical bone. Alternatively, the structure 56can directly contact the cortical bone, such that expansion and/ormanipulation of the structure will cause displacement of the corticalbone. Expansion of the structure 56 within the vertebral body 26 therebymakes it possible to elevate or push broken and compressed bone back toor near its original prefracture position.

[0076] The structure 56 is preferably left inflated within the vertebralbody 26 for an appropriate waiting period, for example, three to fiveminutes, to allow some coagulation inside the vertebral body 26 tooccur. After the appropriate waiting period, the physician collapses andremoves the structure 56. As FIG. 8 shows, upon removal of the structure56, the formed cavity 60 remains in the interior volume 30.

[0077] As FIGS. 9B, 9C, and 9D show, the physician next introduces afilling material 62 into the formed cavity 60 using an appropriatenozzle 114 (as will be described in greater detail later). The fillingmaterial 62 (which FIG. 9A shows after its introduction into the cavity60) can comprise a material that resists torsional, tensile, shearand/or compressive forces within the cavity 60, thereby providingrenewed interior structural support for the cortical bone 28. Forexample, the material 62 can comprise a flowable material, such as bonecement, allograft tissue, autograft tissue, or hydroxyapatite, syntheticbone substitute, which is introduced into the cavity 60 and which, intime, sets to a generally hardened condition. The material 62 can alsocomprise a compression-resistant material, such as rubber, polyurethane,cyanoacrylate, or silicone rubber, which is inserted into the cavity 60.The material 62 can also comprise a semi-solid slurry material (e.g., abone slurry in a saline base), which is either contained within a porousfabric structure located in the cavity 60 or injected directly into thecavity 60, to resist compressive forces within the cavity 60.Alternatively, the material 62 could comprise stents, reinforcing bar(Re-Bar) or other types of internal support structures, which desirablyresist compressive, tensile, torsional and/or shear forces acting on thebone and/or filler material.

[0078] The filling material 62 may also comprise a medication, or acombination of medication and a compression-resistant material, asdescribed above.

[0079] Alternatively, the filling material 62 can comprise a bonefilling material which does not withstand compressive, tensile,torsional and/or shear forces within the cavity. For example, where thepatient is not expected to experience significant forces within thespine immediately after surgery, such as where the patient is confinedto bed rest or wears a brace, the filling material 62 need not be ableto immediately bear load. Rather, the filling material 62 could providea scaffold for bone growth, or could comprise a material whichfacilitates or accelerates bone growth, allowing the bone to heal over aperiod of time. As another alternative, the filling material couldcomprise a resorbable or partially-resorbable source of organic orinorganic material for treatment of various bone or non-bone-relateddisorders including, but not limited to, osteoporosis, cancer,degenerative disk disease, heart disease, acquired immune deficiencysyndrome (AIDS) or diabetes. In this way, the cavity and/or fillermaterial could comprise a source of material for treatment of disorderslocated outside the treated bone.

[0080] In an alternative embodiment, following expansion, the expandablestructure 56 can be left in the cavity 60. In this arrangement, flowablefilling material 62 is conveyed into the structure 56, which serves tocontain the material 62. The structure 56, filled with the material 62,serves to provide the renewed interior structural support function forthe cortical bone 28.

[0081] In this embodiment, the structure 56 can be made from an inert,durable, non-degradable plastic material, e.g., polyethylene and otherpolymers. Alternatively, the structure 56 can be made from an inert,bio-absorbable material, which degrades over time for absorption orremoval by the body.

[0082] In this embodiment, the filling material 62 itself can serve asthe expansion medium for the structure 56, to compact cancellous boneand form the cavity 60, to thereby perform both compaction and interiorsupport functions. Alternatively, the structure 56 can be first expandedwith another medium to compact cancellous bone and form the cavity 60,and the filling material 62 can be subsequently introduced after theexpansion medium is removed from structure 56 to provide the interiorsupport function. As another alternative, the filling material couldcomprise a two-part material including, but not limited to, settablepolymers or calcium alginate. If desired, one part of the filling,material could be utilized as the expansion medium, and the second partadded after the desired cavity size is achieved.

[0083] The structure 56 can also be made from a permeable,semi-permeable, or porous material, which allows the transfer ofmedication contained in the filling material 62 into contact withcancellous bone through the wall of the structure 56. If desired, thematerial can comprise a membrane that allows osmotic and/or particulatetransfer through the material, or the material can comprise a materialthat allows the medication to absorb into and/or diffuse through thematerial. Alternatively, medication can be transported through a porouswall material by creating a pressure differential across the wall of thestructure 56.

[0084] As another alternative, fluids, cells and/or other materials fromthe patient's body can pass and/or be drawn through the material intothe structure for various purposes including, but not limited to,fluid/cellular analysis, bony ingrowth, bone marrow harvesting, and/orgene therapy (including gene replacement therapy).

[0085] B. Bilateral Access

[0086] As FIGS. 10 and 11 show, an enlarged cavity 64, occupyingsubstantially all of the interior volume, can be created by thedeployment of multiple expandable structures 56A and 56B through twolateral separate accesses PLA1 and PLA2, made in opposite lateral sidesof a vertebral body 26. In FIG. 10, the expandable structures 56A and56B are carried by separate tools 48A and 48B at the distal ends ofcatheter tubes 50A and 50B, which are separate and not joined together.

[0087] Expansion of the multiple expandable structures 56A and 56B formstwo cavity portions 64A and 64B (shown in FIG. 11). The cavity portions64A and 64B are transversely spaced within the cancellous bone 32. Thetransversely spaced cavity portions 64A and 64B preferably adjoin toform the single combined cavity 64 (shown in FIG. 11), into which afilling material is injected.

[0088] Alternatively (not shown), the transversely spaced cavityportions 64A and 64B can remain separated by a region of cancellousbone. The filling material is still injected into each cavity portion64A and 64B.

[0089]FIG. 10 shows the structures 56A and 56B to possess generally thesame volume and geometry, when substantially expanded. This arrangementprovides a symmetric arrangement for compacting cancellous bone 32. Agenerally symmetric, enlarged cavity 64 (shown in FIG. 11) results.

[0090] Alternatively, the structures 56A and 56B may possess differentvolumes and/or geometries when substantially expanded, therebypresenting an asymmetric arrangement for compacting cancellous bone 32.A generally asymmetric cavity 66 (see, e.g., FIG. 12) results.

[0091] The selection of size and shape of the structures 56A and 56B,whether symmetric or asymmetric, depends upon the size and shape of thetargeted cortical bone 28 and adjacent internal anatomic structures, orby the size and shape of the cavity 64 or 66 desired to be formed in thecancellous, bone 32. It can be appreciated that the deployment ofmultiple expandable structures 56A and 56B makes it possible to formcavities 64 or 66 having diverse and complex geometries within bones ofall types.

[0092] It has been discovered that compression fracture or collapse ofone vertebral body can occur in combination with compression fracture orcollapse of an adjacent vertebral body or bodies. For example, thefailure of one vertebral body may alter loading of adjacent vertebralbodies, or can cause unequal loading of adjacent vertebral bodies,resulting in failure of one of more of the adjacent bodies as well.Because the factors which weaken and/or cause fracture of one vertebralbody will often weaken and/or affect other vertebral bodies within thespinal column, these adjacent vertebral bodies are susceptible tofracture and/or collapse. In a similar manner, the treatment of acompression fracture of a single vertebral body may alter the loading ofthe adjacent vertebral bodies, possibly resulting in failure of one ofmore of the adjacent bodies. The treatment of two or more vertebralbodies during a single procedure may therefore be indicated.

[0093]FIG. 13 shows a procedure treating three adjacent vertebral bodies26A, 26B, and 26C, each with bilateral accesses. As shown, the multiplebilateral procedure entails the deployment of six expandable structures56(1) to 56(6), two in each vertebral body 26A, 26B, and 26C. As FIG. 13shows, expandable structures 56(1) and 56(2) are bilaterally deployed invertebral body 26A; expandable structures 56(3) and 56(4) arebilaterally deployed in vertebral body 26B; and expandable structures56(5) and 56(6) are bilaterally deployed in vertebral body 26C.

[0094] The volume of a given cavity 64 formed in cancellous bone usingmultiple expandable structures (e.g., using a bilateral or other type ofaccess) can be optimized by alternating the expansion of the multipleexpandable structures deployed. For example, in the illustratedembodiment, in each vertebral body, one of the expandable structures56(1) is first expanded, followed by the expansion of the otherexpandable body 56(2).

[0095] When pressure is first applied to expand a given structure 56(1)to 56(6), cancellous bone will begin to compact and/or cortical bonewill begin to displace. A period of time follows in which the pressurewithin the structure 56(1) to 56(6) typically decays, as the cancellousbone relaxes, further compacts and/or cortical bone is furtherdisplaced. Pressure decay in one structure also typically occurs as theother expandable structure within the vertebral body is expanded. Whenpressure is again restored to the structure 56(1) to 56(6), furthercancellous bone compaction and/or cortical bone displacement generallyresults. A further decay in pressure in the structure 56(1) to 56(6)will then typically follow. A decay of pressure will generally followthe application of pressure, until the cancellous bone is compacted adesired amount and/or cortical bone is displaced to a desired position.

[0096] Optimal cavity formation therefore occurs when each expandablestructure 56 (1) to 56 (6) is allowed to expand in a sequential, stepwise fashion. By allowing the pressure in each structure to decay beforeintroducing additional pressure, the peak internal pressure experiencedwithin each structure can be reduced, thereby reducing the potential forfailure of the structure. FIGS. 14A to 14D more particularly demonstratethis step wise sequence of applying pressure to a given pair ofexpandable structures, e.g., 56(1) and 56(2), when deployed bilaterallyin a vertebral body 26A. It should be appreciated, that the step wiseapplication of pressure can also be used when a single expandable bodyis deployed, or when one or more expandable structures are deployed inother than in a lateral fashion, e.g., using a transpedicular,extrapedicular, or anterior access.

[0097] It should also be understood that expandable structuresincorporating non-compliant materials could be used in similar mannersto accomplish various objectives of the present invention. For example,where the expandable structures comprise non-compliant materials, suchstructures could be expanded within the cancellous bone in thepreviously described manner to compress cancellous bone, create a cavityand/or displace cortical bone. Depending upon the density and strengthof the cancellous and/or cortical bone, the described application ofadditional pressure to the structures could cause a similar cycle ofvolumetric growth and pressure decay. Upon reaching maximum capacityand/or shape of the structures, the introduction of additional pressurewould typically result in little volumetric expansion of the structures.

[0098] In FIG. 14A, the expandable structures 56(1) and 56(2) have beenindividually deployed in separate lateral accesses in vertebral body26A. The expandable structures 56(3)/56(4) and 56(5)/56(6) are likewiseindividually deployed in separate lateral accesses in vertebral bodies26B and 26C, respectively, as FIG. 13 shows. Representative instrumentsfor achieving these lateral accesses will be described later.

[0099] Once the expandable structures 56(1) to 56(6) are deployed, thephysician successively applies pressure successively to one expandablestructure, e.g., 56(1), 56(3), and 56(5), in each vertebral body 26A,26B, and 26C. FIG. 14A shows the initial application of pressure tostructure 56(1). Alternatively, the physician can deploy expandablestructures in a single vertebral body, expand those structures asdescribed herein, and then deploy and expand expandable structureswithin another vertebral body. As another alternative, the physician candeploy the expandable structures in a single vertebral body, expandthose structures as described herein, fill the cavities within thatvertebral body, and then deploy and expand expandable structures withinanother vertebral body.

[0100] The pressure in the structures 56(1), 56(3), and 56(5) will, overtime decay, as the cancellous bone in each vertebral body 26A, 26B, and26C relaxes, further compresses and/or cortical bone displaces in thepresence of the expanded structure 56(1), 56(3), and 56(5),respectively. As pressure decays in the structures 56(1), 56(3), and56(5), the physician proceeds to successively apply pressure to theother expandable structures 56(2), 56(4), and 56(6) in the samevertebral bodies 26A, 26B, and 26C, respectively. FIG. 14B shows theapplication of pressure to structure 56(2), as the pressure in structure56(1) decays.

[0101] The pressure in each structure 56(2), 56(4), and 56(6) willlikewise decay over time, as the cancellous bone in each vertebral body26A, 26B, and 26C is compressed in the presence of the expandedstructure 56(2), 56(4), and 56(6), respectively. As pressure decays inthe structures 56(2), 56(4), and 56(6), the physician proceeds tosuccessively apply additional pressure to the other expandablestructures 56(1), 56(3), and 56(5) in the vertebral bodies 26A, 26B, and26C, respectively. The introduction of additional pressure in thesestructures 26(1), 26(3), and 26(5) further enlarges the volume of thecavity portions formed as a result of the first application of pressure.FIG. 14C shows the introduction of additional pressure to structure56(1) as pressure decays in structure 56(2).

[0102] Pressure, once applied, will typically continue to decay in eachstructure 56(1)/56(2), 56(3)/56(4), and 56(5)/56(6), as the cancellousbone relaxes, continues to compact and/or cortical bone is displaced. Aspressure is successively applied and allowed to decay, the volumes ofthe cavity portions also successively enlarge, until desired cavityvolumes have been achieved in the vertebral bodies 26A, 26B, and 26Cand/or desired displacement of cortical bone has been achieved.

[0103] This deliberate, alternating, step wise application of pressure,in succession first to the structures 26(1)/26(3)/26(5) and then insuccession to the structures 26(2)/26(4)/26(6) in the three vertebralbodies 26A/B/C continues until a desired endpoint for each of thevertebral bodies 26A, 26B, and 26C is reached. In one embodiment, thedesired cavity volume is achieved when cancellous bone is uniformly,tightly compacted against surrounding cortical bone. In an alternativeembodiment, desired cavity volume is achieved when a significantpressure decay no longer occurs after the introduction of additionalpressure, such as where substantially all of the cancellous bone hasbeen compressed and/or the cortical bone does not displace further.

[0104] It should be understood that compaction of cancellous bone may benon uniform due to varying factors, including local variations in bonedensity. In addition, it should be understood that desired displacementof cortical bone can be accomplished in a similar manner, either aloneor in combination with compaction of cancellous bone. By utilizingmultiple structures to displace the cortical bone, a maximum amount offorce can be applied to the cortical bone over a larger surface areathereby maximizing the potential for displacement of the cortical bonewhile minimizing damage to the cortical bone from contact with thestructure(s) and/or cancellous bone.

[0105] Once the desired volume for each cavity 64 and/or desireddisplacement of cortical bone in each vertebral body 26A, 26B, and 26Cis reached, the physician begins the task of conveying a selectedfilling material 62 into each formed cavity 64. It should be appreciatedthat the cavities 64 can be filled with filling material 62 essentiallyin any order, and it is not necessary that all expandable structures beexpanded to form all the cavities 64 before the filling material isconveyed into a given cavity.

[0106] In one embodiment, the filling material is conveyed inalternating steps into the cavity portions 64A and 64B of each vertebralbody 26A, 26B, and 26C. In this technique, the cavity volumes 64A formedby the expandable structures 56(1), 56(3), and 56(5) are filled insuccession before the cavity volumes 64B formed by the expandablestructures 56(2), 56(4), and 56(6) are filled in succession.

[0107]FIGS. 15A and 15B show this embodiment of a filling sequence forthe vertebral body 26A. The vertebral bodies 26B and 26C are filled inlike manner. In the vertebral body 26A, the expandable structure 56(1)is deflated and removed. The filling material 62 is then conveyed intothe corresponding cavity portion 64A. Next, in the vertebral body 26B,the expandable structure 56(3) is deflated and removed, and the fillingmaterial 62 conveyed into the corresponding cavity portion 64A. Next, inthe vertebral body 26C, the expandable structure 56(5) is deflated andremoved, and the filling material 62 conveyed into the correspondingcavity portion 64A. The expandable structures 56(2), 56(4), and 56(6)are left inflated within the respective vertebral bodies 26A, 26B, and26C during this portion of the filling process.

[0108] The physician waits for the filling material 62 conveyed into thevertebral bodies 26A, 26B, and 26C to harden. Then, as FIG. 15B showsfor the vertebral body 26A, the expandable structure 56(2) is deflatedand removed. The filling material 62 conveyed into the correspondingcavity portion 64B. Next, in the vertebral body 26B, the expandablestructure 56(4) is deflated and removed, and the filling material 62conveyed into the corresponding cavity portion 64B. Last, in thevertebral body 26C, the expandable structure 56(6) is deflated andremoved, and the filling material 62 conveyed into the correspondingcavity portion 64B. The above sequence allows a single batch of thefilling material 62 to be mixed and expeditiously dispensed to fillmultiple cavities 64.

[0109] In one alternative embodiment, the filling material is conveyedin alternating steps into the cavity portions of each respectivevertebral body prior to filling the next vertebral body. In thistechnique, the expandable structure 56(1) is removed from the vertebralbody, and filling material is conveyed into the corresponding cavityportion 64A. The expandable structure 56(2) is then removed from thevertebral body, and filling material is conveyed into the correspondingcavity portion 64B. If desired, the filling material can be allowed toharden to some degree before the expandable structure 56(2) is removedfrom the vertebral body. The process is then repeated for each remainingvertebral body to be treated. In this embodiment, the vertebral body isdesirably substantially supported by the filling material and/or anexpandable structure during the filling process, which reduces and/oreliminates the opportunity for the cavity to collapse and/or corticalbone to displace in an undesired direction during the filling operation.

[0110] III. Instruments for Establishing Bilateral Access

[0111] During a typical bilateral procedure, a patient lies on anoperating table. The patient can lie face down on the table, or oneither side, or at an oblique angle, depending upon the physician'spreference.

[0112] A. Establishing Multiple Accesses

[0113] 1. Use of Hand Held Instruments

[0114] For each access (see FIG. 16A), the physician introduces a spinalneedle assembly 70 into soft tissue ST in the patient's back. Underradiologic or CT monitoring, the physician advances the spinal needleassembly 70 through soft tissue down to and into the targeted vertebralbody 26. The physician can also employ stereotactic instrumentation toguide advancement of the spinal needle assembly 70 and subsequent toolsduring the procedure. In this arrangement, the reference probe forstereotactic guidance can be inserted through soft tissue and implantedon the surface of the targeted vertebral body. The entire procedure canalso be monitored using tools and tags made of non-ferrous materials,e.g., plastic or fiber composites, such as those disclosed in U.S. Pat.Nos. 5,782,764 and 5,744,958, which are each incorporated herein byreference, which would be suitable for use in a computer enhanced,whole-room MRI environment.

[0115] The physician will typically administer a local anesthetic, forexample, lidocaine, through the assembly 70. In some cases, thephysician may prefer other forms of anesthesia.

[0116] The physician directs the spinal needle assembly 70 to penetratethe cortical bone 28 and the cancellous bone 32 through the side of thevertebral body 26. Preferably the depth of penetration is about 60% to95% of the vertebral body 26.

[0117] The physician holds the stylus 72 and withdraws the stylet 74 ofthe spinal needle assembly 70. As FIG. 16B shows, the physician thenslides a guide pin instrument 76 through the stylus 72 and into thecancellous bone 32. The physician now removes the stylus 72, leaving theguide pin instrument 76 deployed within the cancellous bone 32.

[0118] The physician next slides an obturator instrument 78 over theguide pin instrument 76, distal end first, as FIG. 16C shows. Thephysician can couple the obturator instrument 78 to a handle 80, whichfacilitates manipulation of the instrument 78.

[0119] The physician makes a small incision in the patient's back. Thephysician twists the handle 80 while applying longitudinal force to thehandle 80. In response, the obturator instrument 78 rotates andpenetrates soft tissue through the incision. The physician may alsogently tap the handle 80, or otherwise apply appropriate additionallongitudinal force to the handle 80, to advance the obturator instrument78 through the soft tissue along the guide pin instrument 76 down to thecortical bone entry site. The physician can also tap the handle 80 withan appropriate striking tool to advance the obturator instrument 78 intoa side of the vertebral body 26 to secure its position.

[0120] The obturator instrument 78 shown in FIG. 16C has an outsidediameter that is generally well suited for establishing a lateralaccess. However, if access is desired through the more narrow region ofthe vertebral body 26, e.g., a pedicle 42 (called transpedicularaccess), the outside diameter of the obturator instrument 78 can bereduced (as FIG. 17 shows) . The reduced diameter of the obturatorinstrument 78 in FIG. 17 mediates against damage or breakage of thepedicle 42. The reduced diameter obturator instrument 78 shown in FIG.17 includes a pointed tip 82 to help secure its position againstcortical bone 28. It should be understood that the disclosed methods anddevices are well suited for use in conjunction with other approachpaths, such as pedicular, extra-pedicular, posterolateral and anteriorapproaches, with varying results.

[0121] The physician then proceeds to slide the handle 80 off theobturator instrument 78 and to slide a cannula instrument 84 over theguide pin instrument 76 and, further, over the obturator instrument 78.If desired, the physician can also couple the handle 80 to the cannulainstrument 84, to apply appropriate twisting and longitudinal forces torotate and advance the cannula instrument 84 through soft tissue ST overthe obturator instrument 78. When the cannula instrument 84 contactscortical bone 28, the physician can appropriately tap the handle 80 witha striking tool to advance the end surface into the side of thevertebral body 26 to secure its position.

[0122] When a reduced diameter obturator 78 is used, as shown in FIG.17, the cannula instrument 84 can carry a removable inner sleeve 86 (asFIG. 17 also shows) to center the cannula instrument 84 about thereduced diameter obturator instrument 78 during passage of the cannulainstrument 84 to the treatment site.

[0123] The physician now withdraws the obturator instrument 78, slidingit off the guide pin instrument 76, leaving the guide pin instrument 76and the cannula instrument 84 in place. When a reduced diameterobturator instrument 78 is used, the physician can remove the innercentering sleeve 86.

[0124] As FIG. 16D shows, the physician slides a drill bit instrument 88over the guide pin instrument 76, distal end first, through the cannulainstrument 84, until contact between the machined or cutting edge 90 ofthe drill bit instrument 88 and cortical bone 28 occurs. The physicianthen couples the drill bit instrument 88 to the handle 80.

[0125] Guided by X-ray (or another external visualizing system), thephysician applies appropriate twisting and longitudinal forces to thehandle 80, to rotate and advance the machined edge 90 of the drill bitinstrument 88 to open a lateral passage PLA through the cortical bone 28and into the cancellous bone 32. The drilled passage PLA preferablyextends no more than 95% across the vertebral body 26.

[0126] As FIG. 18A shows, the drill bit instrument 88 can include aflexible shaft portion 92 to aid in its manipulation. The flexible shaftportion 92 allows the cutting edge 90 of the instrument 88 to flexrelative to the axis of the instrument. As FIG. 18A also shows, thecannula instrument 84 can, if desired, include a deflector element 94 onits distal extremity, to flex the flexible shaft portion 92 and guidethe cutting edge 90 along a desired drill axis. Desirably, in such aflexible embodiment the drill bit instrument 88 is made of a flexibleplastic material, e.g., polyurethane, or a flexible metal materialencapsulated in or surrounding a plastic material, to possess sufficienttorsional rigidity to transmit rotating cutting force to bone.

[0127] Alternatively, as FIG. 18B shows, the drill bit instrument 88 caninclude an interior lumen 180 to accommodate passage of a guide wire182. In this arrangement, the flexible shaft portion 92 conforms to thepath presented by the guide wire 182. The guide wire 182, for example,can be pre-bent, to alter the path of the cutting edge 90 after itenters the vertebral body. Alternatively, the guide wire can be made ofmemory wire, shape memory alloys (including nickel-titanium, copper oriron based alloys, to name a few) , or comprise a self-steering guidingcatheter.

[0128] Still alternatively, as FIG. 18C shows, the drill bit instrument88 itself can carry interior steering wires 184. The steering wires 184are operated by the physician using an external actuator 186, to deflectthe flexible shaft portion 92, and with it the cutting edge, without aidof a guide wire and/or cannula instrument 84.

[0129] Further details regarding the formation of cavities withincancellous bone, which are not symmetric with relation to the axis of avertebral body, can be found in U.S. Pat. No. 5,972,018, entitled“Expandable Asymmetric Structures for Deployment in Interior BodyRegions,” which is incorporated herein by reference.

[0130] Once the passage PLA in cancellous bone 32 has been formed, thephysician removes the drill bit instrument 88 and the guide pininstrument 76, leaving only the cannula instrument 84 in place, as FIG.16E shows. The passage PLA made by the drill bit instrument 88 remains.Subcutaneous lateral access to the cancellous bone 32 has beenaccomplished.

[0131] The physician repeats the above described sequence of steps, asnecessary, to form each access desired. In FIG. 13, six accesses aremade.

[0132] 2. Using Composite Hand Held Instruments

[0133] Other forms of hand held instruments may be used to provideaccess.

[0134] For example, FIGS. 27 and 28 show a composite instrument 310 thatcan be used for this purpose. The composite instrument 310 includes atrocar instrument 320 and a cannula instrument 340. The compositeinstrument 310 also includes a composite handle 312 comprising a firsthandle 322 and a second handle 342. The composite handle 312 aids aphysician in manipulating the composite instrument 310. Still, as FIGS.29A and 29B show, a physician can also desirably use the first handle322 to independently manipulate the trocar instrument 320 or the secondhandle 342 to independently manipulate the cannula instrument 340 duringuse.

[0135] The trocar instrument 320 comprises a trocar 330 having a distalend that is tapered to present a penetrating surface 334. In use, thepenetrating surface 334 is intended to penetrate soft tissue and/or bonein response to pushing and/or twisting forces applied by the physicianat the first handle 322, or the composite handle 312.

[0136] The cannula instrument 340 performs the function of the cannulainstrument 84 previously described, but also includes the handle 342,which mates with the handle 322 to form the composite handle 312. Inthis embodiment, the cannula instrument 84 is desirably somewhat largerin diameter than and not as long as the trocar 330. The cannulainstrument 84 includes an interior lumen 344 that is sized to accept thetrocar 330. The size of the interior lumen 344 desirably allows thecannula instrument 84 to slide and/or rotate relative to the trocar 330,and vice versa. The distal end 354 of the cannula instrument 84 presentsan end surface 360 that desirably presents a low-profile surface, whichcan penetrate soft tissue surrounding the trocar 330 in response topushing and/or twisting forces applied at the composite handle 312 orthe second handle 342.

[0137] In use, as shown in FIG. 30, the physician directs the compositeinstrument 310 such that the trocar 330 and the cannula instrument 84penetrate the cortical bone and the cancellous bone of the targetedvertebra. If desired, the physician can twist the composite handle 312while applying longitudinal force to the handle 312. In response, thepenetrating end surface 334 of the trocar 330, and the end surface ofthe cannula instrument 84 rotate and penetrate soft tissue and/or bone.

[0138] If penetration through the cortical bone and into the cancellousbone is not achievable by manual advancement of the composite instrument310, a physician can continue penetration by gently striking a strikingplate 314 on the composite handle 312 with a blunt instrument such as asurgical hammer (not shown), or otherwise applying appropriateadditional longitudinal force to the composite handle 312, to advancethe distal end 334 of the trocar 330 and the end surface of the cannulainstrument 84.

[0139] If desired, the physician can utilize a spinal needle assembly70, as already described, to initially access the vertebral body. Inthis arrangement, the composite instrument 310 is later guided throughsoft tissue and into the targeted vertebra body along the stylet 74,which (in this arrangement) passes through an interior lumen in thetrocar 330 (not shown). Once the trocar 330 has sufficiently penetratedcortical bone, the physician can withdraw the stylet 74, therebyarriving at the step in the procedure shown in FIG. 30.

[0140] After penetrating the cortical bone, the physician may continueadvancing the composite instrument 310 through the cancellous bone ofthe vertebral body to form the passage through the cancellous bone, asalready described. The trocar 330 may then be withdrawn from the cannulainstrument 84. The cannula instrument 84 remains to provide access tothe passage formed in the interior of the vertebral body, in the mannerpreviously described.

[0141] Alternatively, after penetrating the cortical bone, the physicianmay choose to withdraw the trocar 330 from the cannula 50 and form thepassage in the cancellous bone using a drill bit instrument 88, as FIG.31 shows. In such a case, the physician removes the trocar 330 and, inits place, advances the drill bit instrument 88 through the cannulainstrument 84, as FIG. 31 shows.

[0142] With the removal of the drill bit instrument 88, access to thecancellous bone has been accomplished.

[0143] Further details about the structure and use of the compositeinstrument 310 are found in copending U.S. patent application Ser. No.09/421,635, filed Oct. 19, 1999, and entitled “Hand-Held Instrumentsthat Access Interior Body Regions,” which is incorporated herein byreference.

[0144] 3. Breach Prevention and Plugging

[0145] To create access into the vertebral body in the manners shown inFIGS. 16A to 16D, the physician typically advances a stylet 74 of thespinal needle assembly 70 and also the cutting edge of the drill bitinstrument 88 a significant distance into the cancellous bone 32, asFIGS. 16B and 16D show, toward cortical bone 28 on the anterior wall ofthe vertebral body 26. The density of the cancellous bone 32 desirablyoffers resistance to the passage of these instruments, to therebyprovide tactile feed back to the physician, which aids in guiding theirdeployment. Still, the density of cancellous bone 32 is not uniform andcan change abruptly. Even with the utmost of care and skill, it ispossible that the stylet 74 or the cutting edge 90 can slide into andpoke through cortical bone 28 in the anterior wall of the vertebral body26. This can create a hole or breach B in the anterior cortical wall 28of the vertebral body 26, as FIG. 19 shows.

[0146] To aid in the advancement of the cutting edge 90 throughcancellous bone 32 (see FIG. 20A), the drill bit instrument 88 mayinclude a mechanical stop 96. In use, the mechanical stop 96 abutsagainst the proximal end of the cannula instrument 84. The abutmentstops further advancement of the drill bit instrument 88 into theinterior of the vertebral body 26.

[0147] The location of the mechanical stop 96 may be adjustable, toprovide variable lengths of advancement, depending upon the size of thevertebral body 26 or other bone volume targeted for treatment.

[0148] Alternatively, or in combination, the drill bit instrument 88 mayinclude markings 98 located along its length at increments from itsterminus. The markings 98 register with the exposed proximal edge of thecannula instrument 84 (see FIG. 20A), to allow the physician to remotelygauge the position of the instrument in the vertebral body 26.

[0149] To aid the advancement of the stylet 74, the trocar 330, or thedrill bit instrument 88 within the vertebral body, without breach of theanterior cortical wall, the physician can also make use of a corticalwall probe 140, as shown in FIG. 20B. The cortical wall probe 140comprises a generally rigid stylet body 142 having a blunt distal tip144, which desirably cannot easily pierce the anterior cortical wall ofthe vertebral body. In the illustrated embodiment, the blunt distal tip144 comprises a rounded ball shape.

[0150] The cortical wall probe 140 can be deployed through the formedaccess opening before any significant penetration of cancellous boneoccurs. For example, after the access opening is formed using the spinalneedle assembly 70, but before the stylus 72 and stylet 74 are advanceda significant distance into cancellous bone, the stylet 74 can bewithdrawn and, instead, the cortical wall probe 140 advanced through thestylus 72. The physician advances the cortical wall probe 140 throughcancellous bone, until the physician tactilely senses contact betweenthe blunt distal tip 144 and the anterior cortical wall. Desirably, theprobe 140 is radiopaque, so that its advancement through cancellous boneand its contact with the anterior cortical wall within the vertebralbody can be visualized, e.g., either by x-ray or real time fluoroscopyor MRI. Using the cortical wall probe 140, the physician can gauge thedistance between the access opening into the vertebral body and theanterior cortical wall, in a manner that avoids penetration of theanterior cortical wall.

[0151] The cortical wall probe 140 can carry length markings 146 on itsproximal region, which, when contact with the anterior cortical walloccurs and/or is imminent, indicate the distance a subsequent instrumentcan be advanced down the stylus 72 (or cannula instrument 84) beforecontacting the anterior cortical wall. The information obtained from thecortical wall probe 140 can also be used to set the mechanical stop 96(previously described), to physically prevent advancement of the trocar330 or drill bit instrument 88 before contact with the anterior corticalwall occurs.

[0152] In the event of a breach or suspected breach of the anteriorcortical wall of the vertebral body, the physician can alternativelyutilize the cortical wall probe 140 to safely and easily determine theexistence and/or extent of a wall breach. Because the distal tip 144 ofthe probe is blunt, the tip 144 desirably will not easily pass throughan intact anterior cortical wall, which allows the physician to “tap”the tool along the inner surface of the anterior cortical wall whilesearching for breaches. Where a wall breach has occurred, and the toolcould pass through the breach, the blunt tip 144 of the tool desirablywill not pierce or damage soft tissues, such as the aorta or majorveins, located forward of the cortical wall. If desired, the blunt tip144 can alternatively be formed of a soft, deformable material such asrubber or plastic.

[0153] If a breach B occurs, a suitable material may be placed into thebreach B to plug it. For example, a demineralized bone matrix material,such as GRAFTON™ material, may be used. The material can be placed,e.g., on the distal end of the obturator instrument 78 or trocar 330.The instrument 78 is deployed carrying the plugging material to theexterior side wall where the breach B occurs. The instrument 78 depositsthe plugging material in the breach B, to thereby close it from theoutside of the vertebral body 26.

[0154] The physician can take steps to counteract undetermined corticalwall breaches, either as may possibly preexist before cavity formationor which may possibly exist after cavity formation. Even if a breach isnot known to exist, the physician can nevertheless elect to insert asuitable plug material) (e.g., GRAFTON™ bone matrix material, orCollagraft™ sheet material, or a mesh-type material) into the vertebralbody, either before or after the structure 56 is expanded. The presenceof a plug material guards against the possibility of leaks, whether theyexist or not. Furthermore, if inserted before the structure 56 isexpanded, the presence of the plug material in the vertebral body canserve to make the distribution of the expansion force of the structure56 more uniform. The presence of the plug material within the vertebralbody as the structure 56 expands can also protect against protrusion ofthe expanding structure 56 through any preexisting breach in thecortical wall as well as any breaches created during expansion of thestructure 56, or can otherwise protect weakened cortical walls duringexpansion of the structure 56.

[0155] 4. Cannula Locking Device

[0156] Referring to FIG. 26A, a cannula locking device 190 can be usedto aid in stabilizing the cannula instrument 84 while accessing avertebral body. The locking device 190 can be variously constructed.

[0157] In the embodiment shown in FIG. 26A, the locking device 190includes a generally planar base 192. In use, the base 192 rests upon askin surface surrounding the targeted incision site. If desired, thebase 192 can incorporate an adhesive (not shown) to secure the base tothe patient's skin or to other material located at or near the surgicalsite.

[0158] An instrument grip 194 is supported on the base 192. Theinstrument grip 194 includes a channel 218 which slidingly receives thecannula instrument 84, which, in this embodiment, is intended to beplaced into the grip 194 distal end first. A ring 220, threaded to thegrip 194, can be provided to tighten the channel 218 about the cannulainstrument 84, to thereby prevent axial movement of the cannulainstrument 84 within the channel 218.

[0159] The grip 194 also includes a tenon 196, which fits within amortise 198 on the base 192. The mortise 198 and tenon 196 together forma joint 200. The grip 194 pivots 360-degrees in transverse and/ororbital paths within the joint 200.

[0160] The mortise 198 is bounded by a collet 210, about which aretaining ring 202 is threadably engaged. Twisting the ring 202 in onedirection (e.g., clockwise) closes the collet 210 about the tenon 196,locking the position of the grip 194 relative to the base 192. Twistingthe ring 202 in an opposite direction opens the collet 210 about thetenon 196, freeing the grip 194 for pivotal movement relative to thebase 192.

[0161] To use the device 190, the physician manipulates the cannulainstrument 84 held in the grip 194 into a desired axial and angularorientation. The physician thereafter locks the grip 194 (tightening therings 202 and 220) to hold the cannula instrument 84 in the desiredaxial and angular orientation. The physician can manipulate and lock thecannula instrument 84 in any desired order, either before or afterpassage of the instrument 84 through the skin, and/or before or afterpassage of the instrument 84 through cortical bone, or combinationsthereof. Markings 204 on the grip 194 and base 192 allow the physicianto gauge movement of the grip 194 relative to the base 192 or anotherreference point.

[0162] The locking device 190 is preferably made from a material that isnot highly radiopaque, e.g., polyurethane or polycarbonate. The device190 will therefore not obstruct fluoroscopic or x-ray visualization ofthe cannula instrument 84 during use.

[0163] When locked, the device 190 prevents unintended movement of thecannula instrument 84 along the skin surface. The likelihood that thecannula instrument 84 will be bent or its position inadvertently shiftedduring use is thereby mitigated. The device 190 also allows thephysician to remove his/her hands from the instrument 84, e.g., to allowclear fluoroscopy or x-ray visualization. The device 190 obviates theneed for other types of clamps that are radiopaque or are otherwise notwell suited to the task.

[0164] As FIG. 26B shows, in an alternative embodiment, the retainingring 202 can be loosened to a point that opens the collet 210 enough tofree the grip 194 from the base 192. In this arrangement, the grip 194comprises members 206 and 208 that can be split apart when separatedfrom the confines of the collet 210. The cannula instrument 84 can becaptured between the spit-apart members 206 and 208 as they are fittedback together, obviating the need to load the cannula instrument 84distal end first in the grip 194.

[0165] When fitted together, the tenon 196 can be returned to themortise 198. The retaining ring 202 can be tightened sufficiently toclose the collet 210 about the tenon 196, forming the joint 200. Furthertightening of the retaining ring 202 about the mortise 198 closes thejoint 200 (as before described), locking the grip 194 a desiredorientation relative to the base 192. Subsequent loosening of theretaining ring 202 permits separation of the grip 194 from the base 192,so that the members 206 and 208 can be split apart to free the cannulainstrument 84. In one embodiment, the grip 194 can contact the cannuladirectly, such that the cannula is substantially “locked” in positionwhen the grip 194 is compressed against the cannula. In an alternateembodiment, an O-ring (not shown) can be located within the grip 194,such that compression of the grip causes the O-ring to push against thecannula, desirably substantially “locking” the cannula in positionwithin the grip 194.

[0166] B. Forming the Cavities

[0167] Once the accesses PLA have been formed, the physician advancesindividual catheter tubes 50 through the cannula instrument 84 andpassage of each access, into the interior volume of the associatedvertebral body 26A, 26B, and 26C. FIG. 16F shows this deployment invertebral body 26A.

[0168] The expandable structures 56(1) to 56(6) are then expanded in thealternating, step wise fashion as already described. The compressionforms the interior cavity 64 in each vertebral body 26A, 26B, and 26C.

[0169] As FIGS. 4 and 5 show, the expandable structure 56 can carry atleast one radiopaque marker 102, to enable remote visualization of itsposition within the vertebral body 26. In the illustrated embodiment,the expandable structure 56 carries a radiopaque marker 102 on both itsdistal and proximal end.

[0170] As before described, when fluoroscopic or CT visualization isused to monitor expansion of the structure 56, the fluid used to causeexpansion of the structure 56 is preferably rendered radiopaque (e.g.,using Renografin™ material). The visualization instrument (e.g., a C-armfluoroscope) is typically positioned on the operating table to viewlaterally along one side of the spinal column. The presence ofradiopaque expansion medium in a expanded structure 56 in the vertebralbody 26 can block effective visualization elsewhere in the vertebralbody, e.g., where cavity formation using another structure 56 or wherevertebroplasty or another form of treatment is intended to occur.

[0171] Visualization can be facilitated under these circumstances byremoval or dilution of the radiopaque medium within the structure 56after the structure is expanded to create a cavity.

[0172] In one embodiment (see FIG. 32), an exchange chamber 400 isprovided, which is divided into two compartments 402 and 404 by a piston414 that is movable by pressure upon a plunger 420. Dual lumens 406 and408 communicate with the interior of the structure 56. The lumen 406communicates with the source 422 of radiopaque medium 410 to convey themedium 410 into the structure 56 to cause expansion and cavity formationin the first instance. The lumen 406 also communicates with thecompartment 402 on one side of the piston 414.

[0173] The other compartment 404 of the chamber 400 contains areplacement expansion medium 412. The replacement medium 412 is free ofa radiopaque material or, if desired, can contain a partially-radiopaquematerial. The lumen 408 communicates with this compartment 404.

[0174] After expansion of the structure 56 with the radiopaque medium410, movement of the piston 414 will draw the radiopaque medium 410 fromthe structure 56 (through lumen 402). Simultaneously, the piston 414will displace the radiopaque-free medium 412 into the structure 56(through lumen 404). Piston movement exchanges the radiopaque medium 410with the radiopaque-free medium 412, without collapsing the structure56.

[0175] In an alternative embodiment, an ion exchange material for theradiopaque material in the medium 410 (e.g., iodine) can be introducedinto the radiopaque medium 410 contained within the structure 56. Theion exchange material selectively binds the radiopaque material,diluting the radiopaque qualities of the medium 410. The radiopaquemedium 410 can be circulated through an ionic exchange chamber outsidethe structure 56, or the ion exchange material can be introduced intothe structure 56 through an interior lumen within the structure 56itself.

[0176] Alternatively, a material that causes precipitation of radiopaquematerial can be introduced into the radiopaque medium 410 within thestructure 56 (e.g., through an interior lumen). The precipitationselectively causes the radiopaque material to settle downward within thestructure 56, out of the lateral visualization path, thereby dilutingthe radiopaque qualities of the medium 410.

[0177] As FIG. 5 shows, the expandable structure 56 can also include aninterior tube 104. The interior tube 104 contains an interior lumen 106that passes through the expandable structure 56.

[0178] The interior lumen 106 can be used to convey a flowable materialor liquid, e.g. saline or sterile water, to flush materials free of thedistal region of the structure 56, when in use. The interior lumen 106can also be used to aspirate liquid material from the interior of thevertebral body 26 as the procedure is performed. The interior lumen 106can also be used to introduce a thrombogenic material, e.g., a clottingagent, into contact with cancellous bone 32 during the procedure. Theexpandable structure 56 itself can be also dipped into thrombin prior toits introduction into the vertebral body 26 to facilitate in situcoagulation.

[0179] The interior lumen 106 can also be sized to receive a stiffeningmember or stylet 108 (see FIG. 5). The stylet 108 keeps the structure 56in a desired distally straightened condition during its passage throughthe cannula instrument 84. Once the structure 56 is located in thedesired location within cancellous bone, the physician can remove thestylet 108, and thereby open the interior lumen 106 for conveyance ofliquids to and from cancellous bone, as just described.

[0180] The stylet 108 can also have a preformed memory, to normally bendits distal region. The memory is overcome to straighten the stylet 108when passed through the cannula instrument 84. However, as the structure56 and stylet 108 advance free of the cannula instrument 84, passinginto cancellous bone 32, the preformed memory bends the stylet 108. Thebent stylet 108 shifts the axis of the structure relative to the axis ofthe access path PLA. The prebent stylet 108, positioned within theinterior of the structure 56, aids in altering the geometry of thestructure 56 to achieve a desired orientation when deployed for use.

[0181] If the stylet 108 is comprised of a shape memory alloy), such asnickel-titanium(Nitinol), copper or iron based alloys, the distal end ofthe stylet 108 can be set to a prebent “parent shape,” and thensubsequently bent to a substantially straight shape for introductioninto the vertebral body. When the stylet 108 is in its desired position,and bending of the distal end is desired, heat can be applied to theproximal end of the stylet 108, which desirably will cause the distalend of the stylet 108 to assume its parent shape in a known manner.Alternatively, the stylet 108 can be comprised of a shape memoryallowing material having a transition temperature at or below human bodytemperature. Such a stylet 108 can be cooled prior to and/or duringintroduction into the human body, and once in the proper position, thecooling source can be removed, and the patient's body heat will causethe stylet 108 to assume its pre-bent parent shape. If desired, thestylet can be initially positioned within the vertebral body, with thedistal end deflecting within the cancellous bone, or the distal end canbe deflected during insertion into the vertebral body.

[0182] As FIG. 25 shows, the catheter tube 50 can itself carry a drillbit element 170. The drill bit element 170 may be variously constructed.As shown in FIG. 25, the drill bit element 170 comprises a metal cuttingcap bonded or otherwise mounted on the distal end of the interiorcatheter tube 104, beyond the expandable structure 56. In thisarrangement, the stylet 108 can include a keyed distal end 172, whichmates within an internal key way 174 in the drill bit element 170. Thestylet 108 thereby serves to stiffen the distal end of the catheter tube104, so that torsional and compressive loads can be applied to the drillbit element 170. Alternatively, the interior structure of the cathetertube 104 can be otherwise reinforced to transmit torsional andcompressive load forces to the drill bit element 170. Using the drillbit element 170, the physician can open an access opening in thecortical bone, without use of the separate drill bit instrument 88.

[0183] 1. Desired Physical and Mechanical Properties for the ExpandableStructure

[0184] The material from which the structure 56 is made should possessvarious physical and mechanical properties to optimize its functionalcapabilities to compact cancellous bone. Important properties are theability to expand its volume; the ability to deform in a desired waywhen expanding and assume a desired shape inside bone; and the abilityto withstand abrasion, tearing, and puncture when in contact withcancellous bone.

[0185] 2. Expansion Property

[0186] A first desired property for the structure material is theability to expand or otherwise increase its volume without failure. Thisproperty enables the structure 56 to be deployed in a collapsed, lowprofile condition subcutaneously, e.g., through a cannula, into thetargeted bone region. This property also enables the expansion of thestructure 56 inside the targeted bone region to press against andcompress surrounding cancellous bone, or move cortical bone to aprefracture or other desired condition, or both.

[0187] The desired expansion property for the structure material can becharacterized in one way by ultimate elongation properties, whichindicate the degree of expansion that the material can accommodate priorto failure. Sufficient ultimate elongation permits the structure 56 tocompact cortical bone, as well as lift contiguous cortical bone, ifnecessary, prior to wall failure. Desirably, the structure 56 willcomprise material able to undergo an ultimate elongation of at least50%, prior to wall failure. when expanded outside of bone. Moredesirably, the structure will comprise material able to undergo anultimate elongation of at least 150%, prior to wall failure, whenexpanded outside of bone. Most desirably, the structure will comprisematerial able to undergo an ultimate elongation of at least 300%, priorto wall failure, when expanded outside of bone.

[0188] Alternatively, the structure 56 can comprise one or morenon-compliant or partially compliant materials having substantiallylower ultimate elongation properties, including, but not limited to,kevlar, aluminum, nylon, polyethylene, polyethylene-terephthalate (PET)or mylar. Such a structure would desirably be initially formed to adesired shape and volume, and then contracted to a collapsed, lowerprofile condition for introduction through a cannula into the targetedbone region. The structure could then be expanded to the desired shapeand volume to press against and compress surrounding cancellous boneand/or move cortical bone to a prefracture or desired condition, orboth. As another alternative, the structure could comprise a combinationof non-compliant, partially compliant and/or compliant materials.

[0189] 3. Shape Property

[0190] A second desired property for the material of the structure 56,either alone or in combination with the other described properties, isthe ability to predictably deform during expansion, so that thestructure 56 consistently achieves a desired shape inside bone.

[0191] The shape of the structure 56, when expanded in bone, isdesirably selected by the physician, taking into account the morphologyand geometry of the site to be treated. The shape of the cancellous boneto be compressed and/or cortical bone to be displaced, and the localstructures that could be harmed if bone were moved inappropriately, aregenerally understood by medical professionals using textbooks of humanskeletal anatomy along with their knowledge of the site and its diseaseor injury, and also taking into account the teachings of U.S. patentapplication Ser. No 08/788,786, filed Jan. 23, 1997, and entitled“Improved Inflatable Device for Use in Surgical Protocol Relating toFixation of Bone,” which is incorporated herein by reference. Thephysician is also desirably able to select the desired expanded shapeinside bone based upon prior analysis of the morphology of the targetedbone using, for example, plain film x-ray, fluoroscopic x-ray, or MRI orCT scanning.

[0192] Where compression of cancellous bone and/or cavity creation isdesired, the expanded shape inside bone is selected to optimize theformation of a cavity that, when filled with a selected material,provides support across the region of the bone being treated. Theselected expanded shape is made by evaluation of the predicteddeformation that will occur with increased volume due to the shape andphysiology of the targeted bone region.

[0193] Where displacement of cortical bone is desired, the expandedshape can be chosen to maximize the amount of force the structure exertson cortical bone, maximize force distribution over the largest possiblesurface area of the cortical bone and/or maximize displacement of thecortical bone in one or more desired directions. Alternatively, thestructure can be designed to impart a maximum force on a specific areaof the cortical bone so as to cause desired fracture and/or maximumdisplacement of specific cortical bone regions.

[0194] To aid in selecting a suitable size for the expandable structure56, the trocar 330 of the composite instrument 310 (see FIGS. 27 and 28)can carry an array of grooves or like markings 380, which can be viewedunder fluoroscopic visualization. The markings 380 allow the physicianto estimate the distance across the vertebral body, thereby making itpossible to estimate the desired size of the expandable structure 56.Because the cannula instrument 84 is a relatively thin-walled structure,and the trocar 330 is a relatively thicker solid structure, thephysician is able to visualize the markings 380 by fluoroscopy, evenwhen the markings 380 are inside the cannula instrument 84.

[0195] In some instances, it is desirable, when creating a cavity, toalso move or displace the cortical bone to achieve the desiredtherapeutic result. Such movement is not per se harmful, as that term isused in this Specification, because it is indicated to achieve thedesired therapeutic result. By definition, harm results when expansionof the structure 56 results in a worsening of the overall condition ofthe bone and surrounding anatomic structures, for example, by injury tosurrounding tissue or causing a permanent adverse change in bonebiomechanics.

[0196] If desired, the structure 56 can be used to generate sufficientforce to fracture cortical bone and position the fractured cortical bonein a new orientation and/or into a more desired position. Where the bonehas fractured and/or compressed in the past, and subsequently healed,the present methods and devices can be utilized to safely reposition thecortical bone to a more desired position. For example, where a vertebralcompression fracture has healed in a depressed and/or fracturedposition, the disclosed devices and methods can be utilized tore-fracture and reposition the fractured bone to a more desirableposition and/or orientation. By generating sufficient force to fracturethe bone from the interior, through expansion of an expandable body,only a single access portal through the cortical bone need be formed.

[0197] If desired, the structure could alternatively be used inconjunction with various devices, including but not limited to lasers,drills, chisels or sonic generators (e.g. lithotripers), these devicesbeing used to selectively weaken and/or fracture cortical bone alongdesired lines and/or in a desired manner. Once the targeted corticalbone is sufficiently weakened, the structure 56 can be used to fracturethe bone and/or reposition the cortical bone to a new orientation and/orinto a more desired position.

[0198] In a similar manner, the structure 56 can be used to fracture andreposition a portion of the cortical bone, such as where the bone hasgrown and/or healed in a deformed condition. For example, in a patienthaving severe scoliosis (e.g., osteopathic scoliosis), the vertebralcolumn may be laterally curved due to bone deformation. The presentmethods and devices can be utilized to safely fracture and/or repositionthe cortical bone to a more desired position. If desired, sections ofthe bone can be scored, weakened and/or pre-fractured by various devicesincluding, but not limited to, sharp knives, saws, awls, drills, lasersand/or lithotripters, creating desired lines along which the bone willtend to fracture. The depressed sections of the vertebral body candesirably be elevated and reinforced, thereby reducing the lateral curveof the vertebral column and preventing further lateral deformation ofthe spine. By fracturing and/or displacing only a portion of thecortical bone, the present methods and devices minimize unnecessarymuscular-skeletal trauma while permitting treatment of the disease.

[0199] As one general consideration, in cases where the bone diseasecausing fracture (or the risk of fracture) is the loss of cancellousbone mass (as in osteoporosis), the selection of the expanded shape ofthe structure 56 inside bone should take into account the cancellousbone volume which should be compacted to achieve the desired therapeuticresult. An exemplary range is about 30% to 90% of the cancellous bonevolume, but the range can vary depending upon the targeted bone region.Generally speaking, compacting less of the cancellous bone volume leavesmore uncompacted, diseased cancellous bone at the treatment site.

[0200] Another general guideline for the selection of the expanded shapeof the structure 56 inside bone is the amount that the targetedfractured bone region has been displaced or depressed. The expansion ofthe structure 56 inside a bone can elevate or push the fracturedcortical wall back to or near its anatomic position occupied beforefracture occurred. Where the structure 56 directly contacts thedepressed cortical bone, and elevates the cortical bone through directcontact with the expanding structure, compaction of cancellous bone maynot be necessary or desired.

[0201] For practical reasons, it is desired that the expanded shape ofthe structure 56 inside bone, when in contact with cancellous bone,substantially conforms to the shape of the structure 56 outside bone,when in an open air environment. This allows the physician to select inan open air environment a structure having an expanded shape desired tomeet the targeted therapeutic result, with the confidence that theexpanded shape inside bone will be similar in important respects.

[0202] In some instances, it may not be necessary or desired for thestructure to predictably deform and/or assume a desired shape duringexpansion inside bone. Rather, it may be preferred that the structureexpand in a substantially uncontrolled manner, rather than beingconstrained in its expansion. For example, where compaction of weakersections of the cancellous bone is desired, it may be preferred that thestructure initially expand towards weaker areas within the bone. In suchcases, the structure can be formed without the previously-describedshape and/or size, and the expanded shape and/or size of the structurecan be predominantly determined by the morphology and geometry of thetreated bone.

[0203] An optimal degree of shaping can be achieved by materialselection and by special manufacturing techniques, e.g., thermoformingor blow molding, as will be described in greater detail later.

[0204] 4. Toughness Property

[0205] A third desired property for the structure 56, either alone or incombination with one or more of the other described properties, is theability to resist surface abrasion, tearing, and puncture when incontact with cancellous bone. This property can be characterized invarious ways.

[0206] One way of measuring a material's resistance to abrasion, tearingand/or puncture is by a Taber Abrasion test. A Taber Abrasion testevaluates the resistance of a material to abrasive wear. For example, ina Taber Abrasion test configured with an H-18 abrasive wheel and a 1 kgload for 1000 cycles (ASTM Test Method D 3489), Texin® 5270 materialexhibits a Taber Abrasion value of approximately 75 mg loss. As anotherexample, under the same conditions Texin® 5286 material exhibits a TaberAbrasion value of approximately 30 mg loss. Typically, a lower TaberAbrasion value indicates a greater resistance to abrasion. Desirably,one embodiment of an expandable structure will comprise material havinga Taber Abrasion value under these conditions of less than approximately200 mg loss. More desirably, the structure will comprise material havinga Taber Abrasion value under these conditions of less than approximately145 mg loss. Most desirably, the structure will comprise material havinga Taber Abrasion value under these conditions of less than approximately90 mg loss. Of course, materials having a Taber Abrasion value ofgreater than or equal to 200 mg loss may be utilized to accomplish someor all of the objectives of the present invention.

[0207] Another way of measuring a material's resistance to abrasion,tearing and/or puncture is by Elmendorf Tear Strength. For example,under ASTM Test Method D 624, Texin® 5270 material exhibits a TearStrength of 1,100 ft/in. As another example, under the same conditions,Texin 5286 exhibits a Tear Strength of 500 lb-ft/in. Typically, a higherTear Strength indicates a greater resistance to tearing. Desirably, analternative embodiment of an expandable structure will comprise materialhaving a Tear Strength under these conditions of at least approximately150 lb-ft/in. More desirably, the structure will comprise materialhaving a Tear Strength under these conditions of at least approximately220 lb-ft/in. Most desirably, the structure will comprise materialhaving a Tear Strength under these conditions of at least approximately280 lb-ft/in. Of course, materials having a Tear Strength of less thanor equal to 150 lb-ft/in may be utilized to accomplish some or all ofthe objectives of the present invention.

[0208] Another way of measuring a material's resistance to abrasion,tearing and/or puncture is by Shore Hardness. For example, under ASTMTest Method D 2240, Texin® 5270 material exhibits a Shore Hardness of70D. As another example, under the same conditions, Texin® 5286 materialexhibits a Shore Hardness of 86A. Typically, a lower Shore Hardnessnumber on a given scale indicates a greater degree of elasticity,flexibility and ductility. Desirably, another alternative embodiment ofan expandable structure will comprise material having a Shore Hardnessunder these conditions of less than approximately 75D. More desirably,the structure will comprise material having a Shore Hardness under theseconditions of less than approximately 65D. Most desirably, the structurewill comprise material having a Shore Hardness under these conditions ofless than approximately 100A. Of course, materials having a ShoreHardness of greater than or equal to 75D may be utilized to accomplishsome or all of the objectives of the present invention.

[0209] It should also be noted that another alternative embodiment of aexpandable structure incorporating a plurality of materials, such aslayered materials and/or composites, may possess significant resistanceto surface abrasion, tearing and puncture. For example, a layeredexpandable structure incorporating an inner body formed of materialhaving a Taber Abrasion value of greater than 200 mg loss and an outerbody having a shore hardness of greater than 75D might possesssignificant resistance to surface abrasion, tearing and puncture.Similarly, other combinations of materials could possess the desiredtoughness to accomplish the desired goal of compressing cancellous boneand/or moving cortical bone prior to material failure.

[0210] 5. Creating a Pre-Formed Structure

[0211] The expansion and shape properties just described can be enhancedand further optimized for compacting cancellous bone by selecting anelastomer material, which also possess the capability of being preformed(i.e., to acquire a desired shape by exposure, e.g., to heat andpressure), e.g., through the use of conventional thermoforming or blowmolding techniques. Candidate materials that meet this criteria includepolyurethane, silicone, thermoplastic rubber, nylon, and thermoplasticelastomer materials.

[0212] In the illustrated embodiment, TEXIN® 5286 polyurethane materialis used. This material is commercially available from Bayer in pelletform. The pellets can be processed and extruded in a tubular shape. Thestructure 56 can be formed by exposing a cut length of the tubularextrusion to heat and then enclosing the heated tube within a mold whilepositive interior pressure is applied to the tube length 60, such as ina conventional balloon forming machine.

[0213] Further details regarding the creation of the expandablestructure 56 can be found in copending U.S. patent application Ser. No.09/420,529, filed Oct. 19, 1999, and entitled “Expandable PreformedStructures For Deployment in Interior Body Regions”, which isincorporated herein by reference.

[0214] 6. Saline Infusion

[0215] In the treatment of crush, compression, or depression fracture,the expandable structure 56 serves to move cortical bone 28 back to itsoriginal or proper anatomic condition. This result can be achieved asthe cavity is formed, by expansion of the structure 56 within cancellousbone 32 to physically move surrounding compressed or depressed corticalbone 28. Alternatively, as previously described, the cortical bone canbe displaced through direct contact with the expanding structure.

[0216] It has been discovered that a localized vacuum condition may becreated within the cavity 64 in response to the deflation and removal ofthe structure 56. The vacuum may abruptly move surrounding cortical bone28, causing pain. The movement of bone after formation of the cavity 64can also take back some of the distance the cortical bone 28 has beendisplaced as a result of expanding the structure 56 to form the cavity64 in the first place. In a vertebral body 26, the vacuum can preventfull restoration of the vertebral body height.

[0217] As FIG. 21 shows, to prevent formation of the vacuum, a flowablematerial or sterile liquid 110, e.g., saline or radiopaque contrastmedium, can be introduced into the cavity 64 before and during deflationof the structure 56 and its removal from the cavity 64. The volume ofliquid 110 introduced into the cavity 64 at this time is not critical,except that it should be sufficient to prevent the formation of asignificant vacuum. For example, a volume of saline equal to or greaterthan the volume of the cavity will typically prevent significant vacuumformation. Alternatively, volumes of saline less than the volume of thecavity can also prevent significant vacuum formation to varying degrees.

[0218] The liquid 110 can be introduced through the interior lumen 106passing through the structure 56, as previously described.Alternatively, a small exterior tube can be carried along the cathetertube 50 or inserted separately through the cannula instrument 84 toconvey vacuum-preventing liquid 110 into the cavity 64.

[0219] Alternatively, air can be used to prevent vacuum formation. Oncepressure used to expand the structure 56 is released, air can passthrough the interior lumen 106 to replace the volume occupied by thecollapsing structure 56. If the rate of air flow through the interiorlumen 106 under ambient pressure is not sufficient to replace the volumeas it is formed, the air flow rate can be augmented by use of a pump.

[0220] C. Filling the Cavities

[0221] Upon formation of the cavities 64 (see FIG. 16G), the physicianfills a syringe 112 with the desired volume of filling material 62, abatch of which has been previously prepared. When using an expandablestructure 56 having a preformed configuration, the cavity volume createdis known. The physician thereby knows the desired volume of material 62to place in the syringe 112 for each cavity portion 64A and 64B formedin the vertebral body 26.

[0222] The physician attaches a nozzle 114 to the filled syringe 112.The physician then proceeds to deflate and remove the expandablestructures 56(1) to 56(6) through the associated cannula instrument 84,in the sequential fashion already described, and to fill the associatedcavity portion 64A/64B with the material 62.

[0223] To fill a given cavity portion 64A/64B (see FIG. 16H), thephysician inserts the nozzle 114 through the associated cannulainstrument a selected distance into the cavity portion, guided, e.g., byexterior markings 116 or by real-time fluoroscope or x-ray or MRIvisualization. The physician operates the syringe 112 to cause thematerial 62 to flow through and out of the nozzle 114 and into thecavity portion. As FIG. 16H shows, the nozzle 114 may posses a uniforminterior diameter, sized to present a distal end dimension thatfacilitates insertion into the vertebral body. To reduce the overallflow resistance, however, the nozzle 114 can possess an interiordiameter (e.g., see FIG. 22A) that steps down from a larger diameter atits proximal region 118 to a smaller diameter near its distal end 120.This reduces the average interior diameter of the nozzle 114 to therebyreduce the overall flow resistance. Reduced flow resistance permits moreviscous material to be conveyed into the vertebral body. The moreviscous material is desirable, because it has less tendency to exudefrom the bone. compared to less viscous materials.

[0224] In addition to the embodiment shown in FIG. 22A, various otherconstructions are possible to create a reduced diameter nozzle or toolfor introducing material into bone. For example, as shown in FIG. 22B, atool 160 can possess an interior lumen 162 that gradually tapers from alarger interior diameter to a smaller interior diameter. Or, as shown inFIG. 22C, a tool 164 can possess an interior lumen 166 that steps from alarger to a smaller interior diameter. An associated cannula instrument168 (see FIG. 22C) may also include a reduced diameter passage, which isdownsized to accommodate the reduced diameter tool and to present lessflow resistance to filling material conveyed through the cannulainstrument.

[0225] The reduced diameter tool may also be used in association with avertebroplasty procedure, which injects cement under pressure into avertebral body, without prior formation of a cavity, as will bedescribed later.

[0226] The filling material 62 may contain a predetermined amount of aradiopaque material, e.g., barium or tungsten, sufficient to enablevisualization of the flow of material 62 into the cavity portion. Theamount of radiopaque material (by weight) is desirably at least 10%,more desirably at least 20%, and most desirably at least 30%. Thephysician can thereby visualize the cavity filling process.

[0227] As material 62 fills the cavity portion, the physician withdrawsthe nozzle 114 from the cavity portion and into the cannula instrument84. The cannula instrument 84 channels the material flow toward thecavity portion. The material flows in a stream into the cavity portion.

[0228] As FIG. 16H shows, a gasket 122 may be provided about the cannulainstrument 84 to seal about the access passage PLA. The gasket 122serves to prevent leakage of the material about the cannula instrument84.

[0229] The physician operates the syringe 112 to expel the material 62through the nozzle 114, first into the cavity portion and then into thecannula instrument 84. Typically, at the end of the syringe injectionprocess, material 62 should extend from the cavity and occupy about 40%to 50% of the cannula instrument 84. Alternatively, the physician canutilize the syringe 112 to fill the lumen of the nozzle 114 and/orcannula instrument 84 with material 62, and then utilize a tampinginstrument 124 to expel the material from the lumen into the vertebralbody.

[0230] When a desired volume of material 62 is expelled from the syringe112, the physician withdraws the nozzle 114 from the cannula instrument84. The physician may first rotate the syringe 112 and nozzle 114, tobreak loose the material 62 in the nozzle 114 from the ejected bolus ofmaterial 62 occupying the cannula instrument 84.

[0231] As FIG. 16I shows, the physician next advances a tampinginstrument 124 through the cannula instrument 84. The distal end of thetamping instrument 124 contacts the residual volume of material 62 inthe cannula instrument 84. Advancement of the tamping instrument 124displaces progressively more of the residual material 62 from thecannula instrument 84, forcing it into the cavity portion. The flow ofmaterial 62 into the cavity portion, propelled by the advancement of thetamping instrument 124 in the cannula instrument 84, serves to uniformlydistribute and compact the material 62 inside the cavity portion, intoother cavities and/or openings within the bone, and into fracture lines,without the application of extremely high pressure.

[0232] The use of the syringe 112, nozzle 114, and the tampinginstrument 124 allows the physician to exert precise control whenfilling the cavity portion with material 62. The physician canimmediately adjust the volume and rate of delivery according to theparticular local physiological conditions encountered. The applicationof low pressure, which is uniformly applied by the syringe 112 and thetamping instrument 124, allows the physician to respond to fill volumeand flow resistance conditions in a virtually instantaneous fashion. Thechance of overfilling and leakage of material 62 outside the cavityportion is significantly reduced.

[0233] Moreover, the tamping instrument 124 will desirably permithighly-controlled injection of material 62 under higher injectionpressures as well. For example, FIG. 32 depicts a material injectioninstrument 500 comprising a reduced diameter nozzle 180 and a stylet182. The stylet 182 is desirably sized to pass through the reduceddiameter nozzle 180. In turn, the nozzle 180 is desirably sized to passthrough the cannula instrument 184. For material strength, the nozzle180 can be formed from a substantially rigid metal material, e.g.,stainless steel or a high strength plastic.

[0234] The stylet 182 includes a handle 192, which rests on the proximalconnector 186 of the nozzle when the stylet 182 is fully inserted intothe nozzle 180. When the handle is rested, the distal ends of the stylet182 and nozzle 180 align. The presence of the stylet 182 inside thenozzle 180 desirably closes the interior bore.

[0235] In use, the nozzle 180 can be coupled to the syringe 104 andinserted through the cannula instrument 184 into a material-receivingcavity (not shown) formed within a bone. Material 62 in the syringe 104is injected into the nozzle 180 where it desirably passes into the bone.When a sufficient amount of material 62 is injected into the bone and/ornozzle 180, the syringe 104 may be removed from the nozzle 180.

[0236] The stylet 182 can then be inserted into the nozzle 180, andadvanced through the nozzle, desirably pressurizing the material 62 andpushing it out of the nozzle 180. In one disclosed embodiment, thestylet 182 has a diameter of approximately 0.118 in. The cross-sectionalarea of this stylet 182 is approximately 0.010936 in2, and the nozzle180 desirably contains approximately 1.5 cc of filler material. In thisembodiment, pushing the stylet 182 into the nozzle 180 with a force offorce of ten (10) pounds can produce a pressure of approximately 914lb-in2 in the filler material 62 within the nozzle 180. In an alternateembodiment, the stylet 182 has a diameter of approximately 0.136 in. Aforce of ten (10) pounds utilized on this stylet can produce a pressureof approximately 688 lb-in2 in the filler material 62 within the nozzle180.

[0237] The nozzle 180 and stylet 182 can be used in a similar manner asa combination ram 183 to push the filler material 62 through the cannulainstrument 184 into the bone. For example, where filler material 62 iswithin the cannula instrument 184, the insertion of the ram 183 into thecannula 184 will desirably displace the material 62, forcing thematerial 62 from the distal end of the cannula 184 into the bone. In oneembodiment, the diameter of the ram 183 is approximately 0.143 in. Inthis embodiment, pushing the ram 183 with a force of ten (10) pounds iscapable of producing a pressure of 622 lb-in2 in the filler material 62within the cannula 184. As the ram 183 advances through the cannula 184,it will desirably displace the filler material 62 in the cannula 184.The ram 183, therefore, acts as a positive displacement “piston” or“pump,” which permits the physician to accurately gauge the preciseamount of filler material 62 that is injected into the bone.

[0238] If the filler material is very viscous, this material willtypically strongly resist being pumped through a delivery system.Generally, the greater distance the filler material must travel throughthe system, the greater the pressure losses will be from such factors asviscosity of the material and frictional losses with the walls. In orderto account for these losses, existing delivery systems typically highlypressurize the filler material, often to many thousands of pounds ofpressure. Not only does this require stronger pumps and reinforcedfittings for the delivery system, but such systems often cannot dispensefiller material in very precise amounts. Moreover, if the fillermaterial hardens over time, the system must produce even greaterpressures to overcome the increased flow resistance of the material.

[0239] The disclosed systems and methods obviate and/or reduce the needfor complex, high pressure injection systems for delivery of fillermaterials. Because the disclosed ram 183 travels subcutaneously throughthe cannula 184, and displaces filler material 62 out the distal end ofthe cannula 184, the amount of filler material being pushed by the ram183 (and the total amount of filler material 62 within the cannula 184)progressively decreases as filler material is injected into the bone.This desirably results in an overall decrease in resistance to movementof the ram during injection. Moreover, because the amount of materialbeing “pushed” by the ram 183 decreases, an increase in the flowresistance of the curing filler material does not necessarily require anincrease in injection pressure. In addition, because the ram 183 travelswithin the cannula 184, and can travel percutaneously to the injectionsite, the filler material need only be “pumped” a short length before itexits the cannula and enters the bone, further reducing the need forextremely high pressures. If injection of additional filler material isrequired, the ram can be withdrawn from the cannula, additional fillermaterial can be introduced into the cannula, and the process repeated.Thus, the present arrangement facilitates injection of even extremelyviscous materials under well controlled conditions. Moreover, byutilizing varying diameters of cannulas, nozzles and stylets in thismanner, a wide range of pressures can be generated in the fillermaterial 62. If desired, the disclosed devices could similarly be usedto inject filler material through a, spinal needle assembly directlyinto bone, in a vertebroplasty-like procedure, or can be used to fill acavity created within the bone.

[0240] If desired, after the physician has filled the cavity withmaterial 62, the physician may choose to continue injecting additionalmaterial 62 into the vertebral body. Depending upon the local conditionswithin the bone, this additional material may merely increase the volumeof the cavity (by further compacting cancellous bone), or may travelinto the compressed and/or uncompressed cancellous bone surrounding thecavity, which may serve to further compress cancellous bone and/orfurther enhance the compressive strength of the vertebral body.

[0241] When the physician is satisfied that the material 62 has beenamply distributed inside the cavity portion, the physician withdraws thetamping instrument 124 from the cannula instrument 84. The physicianpreferably first twists the tamping instrument 124 to cleanly breakcontact with the material 62.

[0242] Once all cavity portions have been filled and tamped in the abovedescribed manner, the cannula instruments 84 can be withdrawn and theincision sites sutured closed. The bilateral bone treatment procedure isconcluded.

[0243] Eventually the material 62, if cement, will harden to a rigidstate within the cavities 64. The capability of the vertebral bodies26A, 26B, and 26C to withstand loads has thereby been improved.

[0244]FIGS. 9B through 9D depict an alternate method of filling a cavity60 formed within a vertebral body. In this embodiment, a cannulainstrument 84 has been advanced through a pedicle 42 of the vertebralbody by, providing access to a cavity 60 formed therein. A nozzle 180 isadvanced into the vertebral body, with the distal tip of the nozzle 180desirably positioned near the anterior side of the cavity 60. Fillermaterial 62 is slowly injected through the nozzle 180 into the cavity60. As injection of filler material 62 continues, the nozzle 180 iswithdrawn towards the center of the cavity 60. See FIG. 9c. Desirably,as the nozzle 180 is withdrawn, the distal tip of the nozzle 180 willremain substantially in contact with the growing bolus of fillermaterial 62. Once the nozzle 180 is positioned near the center of thecavity 60, additional filler material 62 is injected through the nozzle180 to substantially fill the cavity 60. The nozzle is then removed fromthe cavity 60.

[0245] If desired, the nozzle can be attached to a syringe 104 (see FIG.33) containing filler material. In one embodiment, the syringe 104 willcontain an amount of filler material equal to the volume of the cavity60 formed within the vertebral body, with the nozzle containing anadditional 1.5 cc of filler material. In this embodiment, the cavity 60will initially be filled with filler material expelled from the syringe104. Once exhausted, the syringe 104 can be removed from the nozzle 180,a stylet 182 inserted into the nozzle 180, and the remaining fillermaterial within the nozzle 180 pushed by the stylet 182 into thevertebral body. Desirably, the additional filler material from thenozzle 180 will extravazate into the cancellous bone, compressadditional cancellous bone and/or slightly increase the size of thecavity 60.

[0246] The disclosed method desirably ensures that the cavity iscompletely filled with filler material. Because the patient is oftenpositioned front side (anterior side) down during the disclosedprocedures, the anterior section of the cavity is often the lowest pointof the cavity. By initially filling the anterior section of the cavitywith filler material, and then filling towards the posterior side of thecavity, fluids and/or suspended solids within the cavity are desirablydisplaced by the filler material and directed towards the posteriorsection of the cavity, where they can exit out the cannula. In thismanner, “trapping” of fluids within the cavity and/or filler material isavoided and a complete and adequate fill of the vertebral body isensured.

[0247] If desired, the filler material can be allowed to harden and/orcure before injection into the vertebral body. For example, in oneembodiment, the filler material comprises bone cement, which is allowedto cure to a glue or putty-like state before being injected into thecavity. In this embodiment, the cement would desirably have aconsistency similar to toothpaste as the cement begins to extrude fromthe nozzle.

[0248] The selected material 62 can also be an autograft or allograftbone graft tissue collected in conventional ways, e.g., in paste form(see Dick, “Use of the Acetabular Reamer to Harvest Autogenic Bone GraftMaterial: A Simple Method for Producing Bone Paste,” Archives ofOrthopaedic and Traumatic Surgery (1986), 105: 235-238), or in pelletform (see Bhan et al, “Percutaneous Bone Grafting for Nonunion andDelayed Union of Fractures of the Tibial Shaft,” InternationalOrthopaedics (SICOT) (1993) 17: 310-312). Alternatively, the bone grafttissue can be obtained using a Bone Graft Harvester, which iscommercially available from SpineTech. Using a funnel, the paste orpellet graft tissue material is loaded into the cannula instrument 8430. The tamping instrument 124 is then advanced into the cannulainstrument 84 in the manner previously described, to displace the pasteor pellet graft tissue material out of the cannula instrument 84 andinto the cavity portion.

[0249] The selected material 62 can also comprise a granular bonematerial harvested from coral, e.g., ProOsteon™ calcium carbonategranules, available from Interpore. The granules are loaded into thecannula instrument 84 using a funnel and advanced into the cavity usingthe tamping instrument 124.

[0250] The selected material 62 can also comprise demineralized bonematrix suspended in glycerol (e.g., Grafton™ allograft materialavailable from Osteotech), or SRSM calcium phosphate cement availablefrom Novian. These viscous materials, like the bone cement previouslydescribed, can be loaded into the syringe 112 and injected into thecavity using the nozzle 114, which is inserted through the cannulainstrument 84 into the cavity portion. The tamping instrument 124 isused to displace residual material from the cannula instrument 84 intothe cavity portion, as before described.

[0251] The selected material 62 can also be in sheet form, e.g.Collagraft™ material made from calcium carbonate powder and collagenfrom bovine bone. The sheet can be rolled into a tube and loaded by handinto the cannula instrument 84. The tamping instrument 124 is thenadvanced through the cannula instrument 84, to push and compact thematerial in the cavity portion.

[0252] The various instruments just described to carry out a bilateralprocedure can be arranged in one or more prepackage kits 126, 128, and130, as FIG. 23 shows. For example, a first kit 126 can package anaccess instrument group for achieving bilateral access into a singlevertebral body (comprising, e.g., at least one spinal needle instrument70, at least one guide wire instrument 76, at least one obturatorinstrument 78, two cannula instruments 84, and at least one drill bitinstrument 88). Alternatively, the first kit 126 can contain at leastone trocar 330 and two cannula instruments 84, which together form twocomposite instruments 310.

[0253] A second kit 128 can package a cavity forming instrument groupfor the bilateral access (comprising, e.g., two cavity forming tools48). A third kit 130 can package a material introduction instrumentgroup for the bilateral access (comprising, e.g., at least one syringe112, at least one nozzle 114, and at least one tamping instrument 124).Alternatively, the kit 130 can comprise a material introductioninstrument group comprising a syringe 112, a cannula 84 and a tampinginstrument 124 sized to fit within the cannula. The kits 126, 128, and130 also preferably include directions for using the contents of thekits to carry out a desired bilateral procedure, as above described.

[0254] A fourth kit 132 can also be included, to include the ingredientsfor the filling material 62, which, as before explained, may contain apredetermined amount of a radiopaque material, e.g., barium or tungsten,sufficient to enable visualization of the flow of material 62 into thecavity portion. The kit 132 also preferably include directions formixing the material 62 to carry out a desired bilateral procedure, asabove described.

[0255] Of course, it should be understood that the individualinstruments could be kitted and/or sold individually, with instructionson their use. If desired, individual instrument kits could be combinedto form procedure kits tailored to individual procedures and/orphysician preference. For example, a general instrument kit forperforming a single level procedure could comprise a guide wireinstrument 76, an obturator instrument 78, a cannula instrument 84, anda drill bit instrument 88.

[0256] D. Alternative Cavity Formation and Filling Techniques

[0257] A cavity, filled with a compression-resistant material, can becreated within a vertebral body in alternative ways.

[0258] For example (see FIG. 24A), a small diameter expandable body 150can be introduced into a vertebral body through the stylus 72 of aspinal needle assembly 70, or another needle sized approximately 8 to 11gauge. Expanding the small structure 150 compacts cancellous bone toform a desired cement flowpath within the vertebral body and/or abarrier region 152 substantially surrounding the structure 150.Alternatively, a mechanical tamp, reamer, or single or multiple holepuncher can be used to create a desired cement flowpath within thevertebral body and/or compact cancellous bone to form a small barrierregion 152. The desired cement flowpath and/or compacted cancellous bonesurrounding the barrier region 152 will reduce and/or preventextravazation of the flowable material injected outside the vertebralbody.

[0259] A flowable filling material 154, e.g., bone cement, can be pumpedunder high pressure by a pump 156 through the needle 72 into the desiredcement flowpath and/or barrier region 152 (see FIG. 24B) in a volumethat exceeds the volume of the flowpath/barrier region 152. The fillingmaterial 154 pushes under pressure against the compacted cancellousbone, enlarging the volume of the flowpath/barrier region 152 asmaterial 154 fills the flowpath/region 152 (see FIG. 24C). The interiorpressure exerted by the filling material can also serve to move recentlyfractured cortical bone back toward its pre-fracture position. Theflowable material is allowed to set to a hardened condition, aspreviously explained.

[0260] A multiple level procedure can be performed using differenttreatment techniques on different vertebral body levels. For example, ifa given vertebral body layer has developed cracks and experiencedcompression fracture, the cavity-forming and bone lifting techniquespreviously described can be advantageously used. The cavity forming andbone lifting technique can comprise use of one or more expandable largerbodies 56 followed by low pressure introduction of filling material (asshown in FIGS. 10 to 12), or use of one or more smaller expandablebodies 150 followed by high pressure introduction of filling material(as shown in FIGS. 24A to 24C), or use of a combination thereof (e.g.,in a bilateral procedure).

[0261] It may be indicated to treat another vertebral body utilizingvertebroplasty techniques, which have as their objectives thestrengthening of the vertebral body and the reduction of pain. Forexample, where the end plates of the vertebral body have depressed to apoint where an expandable structure cannot be safely inserted and/orexpanded within the vertebral body, bone cement can be injected underpressure through a needle directly into the cancellous bone of thevertebral body (without cavity formation). The bone cement penetratescancellous bone. To reduce flow resistance to the cement, the needle canpossess an increasing interior diameter, as shown in FIGS. 22A, 22B, or22C. The reduced flow resistance makes possible the use of more viscouscement, to thereby reduce the possibility that the cement will exudefrom the vertebral body.

[0262] Different treatment techniques can also be used in differentregions of the same vertebral body. For example, any of the abovedescribed cavity-forming and bone lifting techniques can be applied inone region of a vertebral body, while conventional vertebroplasty can beapplied to another region of the same vertebral body. Such a procedurewould be especially well suited for treatment of scoliosis, aspreviously discussed herein. Alternatively, the various disclosedtechniques can be utilized in separate vertebral bodies within the samespinal column.

[0263] The features of the invention are set forth in the followingclaims.

We claim:
 1. A method for treating bone comprising the steps ofdeploying a unitary support body that carries a bone cutting element andan expandable structure, manipulating the support body to operate thebone cutting element to form an opening in cortical bone, furthermanipulating the support body to insert the expandable structure throughthe opening into bone, and further manipulating the support body toexpand the expandable structure and form a cavity in cancellous bone. 2.A method according to claim 1 wherein the expandable structure, duringexpansion, applies force capable of moving cortical bone.
 3. A methodaccording to claim 1 further including the step of conveying a materialinto the cavity.
 4. A method according to claim 1 further including thestep of conveying a filling material into the cavity.
 5. A methodaccording to claim 1 further including the step of conveying acompression-resistence material into the cavity.
 6. A method accordingto claim 1 further including the step of conveying medication into thecavity.